GaAs doping by rapid thermal diffusion of a laser-deposited elemental Zn source film: Shallow and laterally graded diffusions

Abstract

We present an excimer-laser-based doping process useful for shallow uniform and laterally graded p-type doping of GaAs substrates. Specifically, low power 248-nm pulses from a KrF excimer laser are used to nonthermally photodeposit thin Zn layers (∼3–300 Å) from a dimethylzinc (DMZn) ambient onto selected GaAs surface regions. Uniform exposure of a sample to the laser pulses produces a source film which is laterally uniform in thickness, whereas variations in exposure time across a sample deposit a source film which is laterally graded in thickness. The surface is subsequently capped, and the Zn source is diffused into the GaAs using rapid thermal annealing. Secondary ion mass spectroscopy and spreading resistance measurements indicate that uniformly thick source depositions result in uniform diffusions with shallow junction depths and high surface concentrations. Alternatively, our measurements show that gradations in the dopant source profile translate into laterally graded doping profiles for appropriately chosen source thicknesses and diffusion parameters.